Good point. I think it's a combination of zealot-like intensity and humble open-mindedness which wins the day.
Most people are one or the other (or somewhere in between) but to combine both in one human personality is quite rare. This may be a reason why people find it hard to work around and for such people.
personally i think, the person who can't change his/her mind in light of new facts (which is what seems to be emphasized here) is dangerous.
i have _heard_ / _read_ that steve-jobs was known for changing his mind instantly in the light of new facts.
not sure, why this would be misconstrued as _weak_